The present invention relates to a motor and a rotor.
Conventionally, as a rotor to be used in a motor, a rotor having a so-called Lundell-type structure is known as described in Japanese Patent Laid-Open Publication Nos. 2012-115085 and 2013-99097. Such a rotor includes a plurality of rotor cores which each have a plurality of claw-shaped magnetic poles in the circumferential direction, and are combined together. A field magnet is disposed between the rotor cores in the axial direction so that the claw-shaped magnetic poles alternately function as different magnetic poles. Further, such a rotor is provided so as to be rotatable on the inner side of a stator having a winding. The rotor and the stator are housed in a case, which includes a yoke housing formed into a cylindrical shape with a bottom part and a cover part for closing an opening part of the yoke housing.
In a motor as described above, a yoke housing (a bottom part thereof) which is made of a magnetic body is located on one side in the axial direction of the rotor. This may cause leakage of part of magnetic flux, which is generated from the field magnet of the rotor, to the yoke housing, thereby deteriorating power output characteristics.
Moreover, in a motor as described above, a sensor magnet which rotates integrally with the rotary shaft is disposed on a side part of the Lundell-type rotor in the axial direction. Further, a magnetic detection part is disposed on the stator side (a fixed side such as a housing etc.) so as to face the sensor magnet in the axial direction. The magnet detection part detects the rotation of the sensor magnet.
However, in a Lundell-type motor as described above, the permanent magnet of the rotor is magnetized in the axial direction. For that reason, magnetic flux is likely to leak to the housing side in the axial direction from the rotor. Therefore, magnetic flux leaked to the housing side may affect the magnetic detection part, thereby lowering the detection accuracy. In this case, it is possible to suppress leakage of magnetic flux from the rotor to the housing side (the side of the magnetic detection part) by increasing the clearance in the axial direction between the housing supporting the magnetic detection part and the rotor. However, in this case, the size of the motor in the axial direction inevitably increases.